US7443156B2 - Apparatus and method for identifying defects on objects or for locating objects - Google Patents

Apparatus and method for identifying defects on objects or for locating objects Download PDF

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US7443156B2
US7443156B2 US10/595,897 US59589705A US7443156B2 US 7443156 B2 US7443156 B2 US 7443156B2 US 59589705 A US59589705 A US 59589705A US 7443156 B2 US7443156 B2 US 7443156B2
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signal
phase
received signal
fourier
carrier
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US20070242758A1 (en
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Roland Hoelzl
Michael Hermann
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Prueftechnik Dieter Busch AG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/46—Processing the detected response signal, e.g. electronic circuits specially adapted therefor by spectral analysis, e.g. Fourier analysis or wavelet analysis
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
    • G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
    • G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/043—Analysing solids in the interior, e.g. by shear waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/11—Analysing solids by measuring attenuation of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2412—Probes using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/26—Arrangements for orientation or scanning by relative movement of the head and the sensor
    • G01N29/27—Arrangements for orientation or scanning by relative movement of the head and the sensor by moving the material relative to a stationary sensor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/36—Detecting the response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/42—Detecting the response signal, e.g. electronic circuits specially adapted therefor by frequency filtering or by tuning to resonant frequency
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/44—Processing the detected response signal, e.g. electronic circuits specially adapted therefor
    • G01N29/449—Statistical methods not provided for in G01N29/4409, e.g. averaging, smoothing and interpolation

Definitions

  • the present invention relates to an apparatus and a method which are suitable for locating metallic objects e.g., in the ground, and can also be used for identifying defects on objects.
  • the invention can be used for identifying defects or faults on metallic objects, and here in particular, on ferromagnetic semifinished or finished products.
  • a primary object of the present invention is to provide a device of the generic type for which the outlay required for its production is significantly reduced, and which simultaneously enables more precise and more reliable measurements—as far as possible in conjunction with a reduced energy requirement.
  • the indicated object is achieved, in accordance with the present invention, with the aid of computer driving, by the AC voltage energization of at least one transmitting coil being simultaneously effected by a carrier signal, an essentially amplitude- and/or phase-modulated received signal being received by means of at least one receiving coil, and a demodulation of the received signal being formed using the computer and a Fourier or wavelet transformation method, in such a way that a predefined number of digitally determined measurement results (samples) are fed to such a transformation method, an associated magnitude value and/or phase value is calculated for the frequency of the carrier signal and such a magnitude and/or phase value is used as a direct measure of a present signal strength or phase angle of the demodulated received signal.
  • the transformation method is used to calculate a spectrum, associated magnitude values and/or phase values being calculated for the frequencies of the carrier signal and at least one further frequency component of the spectrum, and the magnitude and/or phase values thus calculated are used as a direct measurement of a present signal strength vector or phase angle vector of the demodulated received signal.
  • One important aspect of the invention is based on the insight that it is possible to use hitherto unused signal sources, either by themselves, or in interaction with signal sources that are known per se and used according to the prior art.
  • the invention additionally provides, inter alia, the following either individually or in combination:
  • the procedure according to the invention provides, for these purposes, an extended demodulation method which is regarded as innovative and differs considerably from a simple rectification method and also significantly from conventional synchronous demodulation methods.
  • the demodulation method may, in this connection, also be used for the evaluation of a greatly reduced subset of the available information. Independently of this, it may be combined with an innovative adaptive filter method.
  • the demodulation method according to the invention may essentially be interpreted as one for amplitude-modulated signals. Such signals are known to occur in conventional radio/broadcast signals. However, the demodulation method is also readily able to identify phase changes on a signal to be demodulated and may then be interpreted as a phase demodulation method.
  • these demodulation methods may also be used in the context of, e.g., eddy current, EMAT or ultrasonic testing on industrially produced test specimens.
  • the demodulation process according to the invention presupposes the existence of a carrier, at least the ability to recover said carrier from associated signal sources.
  • Conventional demodulation methods of the type employed in materials testing are restricted merely to determining the spectral energy density, and if appropriate, the phase angle in the vicinity of the carrier frequency, in particular, that of the adjacent sidebands which typically carry the temporally varying information of interest.
  • the invention provides for additionally determining, if appropriate, also the energy densities (viz.
  • the energy density of a DC component (having the frequency zero) can readily be determined by the method according to the invention.
  • the demodulation operation according to the invention for signals for the purpose of materials testing thus provides for, in contrast to conventional demodulation methods, carrying out of a discrete Fourier transformation, or wavelet transformation or the like, on the basis of a selectable present number of measured values that are determined digitally and temporally progressively.
  • An amplitude or intensity of the carrier that is to say of the carrier signal
  • a first present phase value can simultaneously be calculated in this way.
  • the invention involves taking into account not only the temporal variation of the amplitude or of the phase angle of the carrier, but preferably also the temporal variation of the amplitude or of the phase angle of said harmonics, to be precise individually or in combination with one another. Consequently, in comparison with known methods, a plurality of amplitude and/or phase values are provided which, according to the invention, depending on the application, can be evaluated in additive/subtractive combination(s), or furthermore, also other characteristic values which can be obtained by means of multiplication or division of the original values by one another.
  • a conventional, e.g., synchronous demodulation signal merely provides amplitude and phase information in the region of the carrier frequency components shifted to a frequency value “zero” (principle of synchronous demodulation).
  • a simultaneous provision of such information for higher frequencies is not possible, in principle, by means of conventional synchronous demodulation (cf. FIGS. 8 & 9 ).
  • the method according to the invention is based on the fact that, under appropriate preconditions, not only the information content of the carrier and its proximity can be exhausted and utilized, but likewise and in addition, also the information content of the harmonics of the carrier, to be precise with respect to their temporally variable amplitudes and/or phase angles. If some harmonics of the carrier prove to be temporally constant, this fact can be utilized for comparison and reference purposes. Anticipatory reference is made here to FIG. 2 , which reproduces the spectrum of an eddy current test signal that was generated by means of a commercial test system on a test specimen having a plurality of defects.
  • FIG. 1 is a schematic diagram of the measurement principle generally used
  • FIG. 2 is a plot of averaged spectral components (PSD) of an obtained measurement signal
  • FIG. 3 is a plot of spectral components in the absence of faults
  • FIG. 4 is a plot of spectral components in the presence of a fault
  • FIG. 5 is a plot of spectral components in the absence of faults, with intermittent sampling
  • FIG. 6 is a plot of spectral components in the presence of a fault, with intermittent sampling
  • FIG. 7 is a plot of spectral components in the case of synchronous demodulation, with intermittent sampling, in the absence of faults,
  • FIG. 8 is a plot of spectral components in the case of synchronous demodulation, with intermittent sampling, in the presence of a fault
  • FIG. 9 is a plot of the phase behavior in the case of synchronous demodulation, with intermittent sampling, in the absence of faults,
  • FIG. 10 is a plot of the phase behavior in the case of synchronous demodulation, with intermittent sampling, in the presence of a fault
  • FIG. 11 is a plot of the phase behavior in the case of Fourier demodulation, with intermittent sampling, in the absence of faults,
  • FIG. 12 is a plot of the phase behavior in the case of Fourier demodulation, intermittent sampling, in the presence of a fault
  • FIG. 13 is a plot of an amplitude-modulated time signal
  • FIG. 14 is a schematic diagram of an overall system according to the invention.
  • FIG. 15 is an illustration of a result obtained for a Fourier-demodulated overall signal in the absence of faults
  • FIG. 16 is an illustration of a result obtained for a Fourier-demodulated signal based on intermittent sampling, in the absence of faults,
  • FIG. 17 is an illustration of a Fourier-demodulated overall signal with a fault observed
  • FIG. 18 is an illustration of a result obtained for a Fourier-demodulated signal based on intermittent sampling, with a fault observed, and
  • FIG. 19 is an illustration of a comparative result obtained for Fourier-demodulated signals, in the presence and absence of a fault/defect.
  • FIG. 1 schematically shows part of a test specimen 13 , represented in the form of an industrial semi-finished product (slab), together with a defect 15 that is present there and is to be detected.
  • the test specimen 13 can move—in a manner known per se—at constant or varying speed parameter “v”) past a test station containing at least one transmitting coil 12 (L 1 ) and at least one receiving coil 14 (L 2 ).
  • the at least one transmitting coil 12 is energized suitably in accordance with the concept of the invention, by means of an essentially constant AC voltage (approximately 1-1200 kHz; if appropriate, also special frequencies).
  • An eddy current signal is tapped off as a received signal at the at least one receiving coil 14 .
  • This signal is of the same frequency as the transmitting AC voltage, but may have temporal amplitude fluctuations and/or phase fluctuations caused by on or more defects 15 (cf, FIG. 13 with a single region of reduced amplitude and, if appropriate, altered phase).
  • the spectral component (“PSD”) of a signal which is obtained in such a way and converted by means of Fourier transformation is shown in a semi-logarithmic representation in FIG. 2 .
  • the narrowband line of maximum intensity is to be assigned to the so-called carrier, which in this case has a frequency of 5,000 kHz.
  • the DC component at the frequency 0.0 kHz is significantly lower, and even lower than the intensity of the so-called first and second harmonics (that is to say at 10 kHz and 15 kHz, respectively).
  • diverse further lines are present which are distinctly demarcated from a base level encountered at approximately 0 dB.
  • FIG. 3 represents a similar circumstance to FIG. 2 , but based on a reduced, progressively recorded number of samples from the set of the abovementioned samples which are attributed to defect-free regions of the test specimen examined.
  • the proportional spectral lines appear to be widened on account of the reduced number of samples (only approximately 50,000) in comparison with FIG. 2 .
  • the spectral line for the carrier frequency represents, according to the invention, a signal to be demodulated, both the intensity and the phase angle of this signal being of interest.
  • the ratio of the intensities of the first harmonic to the carrier line and also that of the first harmonic to the second harmonic has changed markedly in comparison with FIG. 2 .
  • FIG. 4 represents a similar circumstance to FIG. 2 , likewise based on a reduced number of samples (approximately 30,000) from the set of the abovementioned samples which are attributed here, however, to an individual defective region of the test specimen examined.
  • the proportional spectral lines likewise appear to be widened, and it becomes clear that the ratio of the intensities of the carrier line, first harmonic and second harmonic, thus the intensities of a signal vector provided by demodulation, has once again changed.
  • FIG. 5 is comparable to with FIG. 3 , but is based on another important aspect of the invention, namely, according to which a comparable representation can be obtained with a significantly reduced outlay on hardware and software if measured values are acquired (sampled) intermittently.
  • the same signal was not evaluated on the basis of consecutively acquired measured values, but rather only on the basis of a drastically reduced subset of samples.
  • only every 97th sample was evaluated in the case shown. As is evident, this results in an information content that is comparable with FIG. 3 , albeit reduced.
  • FIG. 6 which is comparable to with FIG. 4 , that is to say is based on a likewise reduced number of samples.
  • FIG. 6 is comparable to with FIG. 4 , that is to say is based on a likewise reduced number of samples.
  • These are attributed here, however, in a directly comparable manner, to an individual defective region of the test specimen examined. In this case, too, only every 97th sample was progressively used for the signal representation of the demodulated signal. The intensities of the first and second harmonics can be seen besides the carrier line.
  • FIG. 7 which is comparable to FIG. 3 or FIG. 5 , that is to say is likewise based on a further reduced number of samples, shows the following: in the case of a synchronous demodulation which operates with sine and cosine values in pairs and which is based in a comparable manner on progressively and/or intermittently selected samples (here, however, every 96th sample is acquired), the carrier line is merely converted into a DC voltage component (with a time-variable character). Information on any harmonics or the originally present DC component of the signal is no longer present for mathematical reasons, irrespective of whether or not a signal caused by a defect is present.
  • FIG. 8 The counterexample is shown in FIG. 8 , which is also based on progressively but intermittently selected samples (likewise only every 96th sample), but which are attributed to a signal range that is representative of the defect or material damage already shown in FIGS. 4 and 6 .
  • the currently present DC voltage component at the frequency 0 kHz
  • no further spectral lines that can be evaluated are present.
  • phase information based on a synchronous demodulation which is associated with FIGS. 7 and 8 is then shown in FIGS. 9 and 10 , respectively, but this is of little use. All that is represented is that the phase differences of the spectral components appear to have less variance when a defect is absent than when a defect is presently observed.
  • the method according to the invention affords usable advantages here by virtue of the fact that, besides the phase information for the carrier, it is additionally possible to represent specifically that information for the first and second harmonics (cf. the indicating arrows depicted in the figure). This applies to “intermittent” data acquisition, too, which here is again based on, for example, every 97th sample of a signal used, to be precise when the test specimen is free of defects.
  • FIG. 12 shows the conditions if the test specimen has a defect.
  • the overall phase shift shown is insignificant and is to be assigned to a start phase value. What is important above all is that a very significant item of phase information of the second harmonic can be discerned besides the phase angle of the carrier; to an extent, a similar item in the vicinity of the first harmonic (cf. the arrows depicted in the figure) can be seen as well.
  • this phase information can be used for improved detection of objects by battery-operated so-called metal detectors.
  • the “intermittent” data acquisition and mode of operation with undersampling enables a very welcome saving of energy.
  • FIG. 13 shows a schematic diagram—which is merely an example—of the procedure when applying the data acquisition operating intermittently (preferably equidistantly intermittently). It is assumed—as shown—that a carrier voltage “U IN ” having a sinusoidal profile over the time “t” or an associated angular dimension “ ⁇ ” is detected by coil L 2 . The carrier voltage is modified for a short time (cf. time measure 4 e 3 ) in the presence of a fault and then rises to the original value again.
  • the demodulation results obtained in the manner portrayed are obtained for the purpose of materials testing for, e.g., four frequencies including the frequency 0.0 kHz merely by means of a single computational method, namely, e.g., by spectral analysis by means of discrete Fourier transformation, and in this case, requires just a single analog/digital converter for the purpose of signal conversion.
  • the invention does not preclude providing two or more analog/digital converters which operate independently of one another and which are triggered progressively, for the purpose of an increased data throughput.
  • the last-mentioned solution makes it possible to provide A/D converters that operate relatively slowly, and nevertheless to implement rapid data acquisition.
  • said computational method may particularly advantageously be based on the analysis of measurement data that have been obtained in the manner of an undersampling, in particular a temporally equidistant undersampling.
  • FIG. 14 schematically shows a test specimen 13 in the form of an industrial semifinished product (slab) together with a defect 15 to be detected.
  • the test specimen 13 can move at varying speeds (parameter “v”) past a test station containing at least one transmitting coil 12 (symbol: L 1 ) and at least one receiving coil 14 (symbol: L 2 ).
  • the speed of the test specimen is detected by an electronically acting speed pick-up 17 , which permits corresponding electronic signals to be output.
  • an electronic unit or computer 40 having the properties of a signal processor is an essential hardware component of the invention.
  • a counter/timer module 44 may be provided separate from the computer 40 or may be integrated into the latter.
  • the subsystem 60 contains the device—required according to the invention—for generating Fourier transforms (alternatively or equivalently: wavelet transforms) and an apparatus—referred to as a digital filter unit—with filter sets 62 defined in terms of software. These are likewise preferably integrated in the computer 40 and may be implemented in dedicated hardware or, in cost-saving fashion, merely in software that can be executed in the computer.
  • the computer 40 can be linked externally to a keyboard 60 , a display 50 and/or to a local area network (reference symbol “LAN”) or WAN.
  • LAN local area network
  • the timer 44 Even in the stationary, that is to say unmoving, state of the test specimen 13 , the timer 44 generates a time signal having a high frequency stability.
  • the frequency of this time signal can be varied as desired or according to the technical requirements and this time signal is typically available as a square-wave signal such as is known per se for a timer.
  • the square-wave signal is supplied to a generator 48 ′ with a predefined frequency.
  • the generator 48 ′ generates from this either a square-wave signal or a sinusoidal signal, preferably with an adjustable amplitude. (A square-wave signal has, in a manner known per se, odd-numbered harmonics that can advantageously be used here).
  • the generated signal is passed to an optionally provided curve shaper KF and a power amplifier PA, which may be combined in a unit 42 .
  • the power amplifier is suitable for energizing the transmitting coil 12 . Consequently, an eddy current field is induced in the test specimen 13 in a manner known per se.
  • the eddy current field is registered by the schematically shown receiving coil 14 —which may also be formed, according to the prior art, as a differential coil set or the like—and is fed as an AC voltage to the AID converter 32 already mentioned, if appropriate via one or more bandpass filters 18 ′, and preferably, via at least one (preferably adjustable) preamplifier 16 .
  • the A/D converter has a resolution of typically 18 bits or better, preferably 22 bits or better.
  • a resolution of 12 bits is also taken into consideration, particularly if approximately 1000 or more samples in each case are fed to a Fourier transformation.
  • the A/D converter 32 is preferably able to carry out much more than 500 analog/digital conversions per second.
  • a defect 15 is present in the test specimen, a modified eddy current field results which induces an AC voltage that is altered in amplitude and/or phase in the receiving coil 14 .
  • the performance of the method according to the invention depends, to a certain extent, on the performance of the A/D converter or A/D converters used. In this case, the resolution thereof (in bits) is also of importance besides the minimum conversion time. Otherwise, according to the invention, there is a considerable configurational possibility with regard to a sampling scheme to be used; that is to say the times at which the signal supplied by the coil L 2 is, or is intended, to be evaluated (sampled). Only a number of samples of more than 3, better more than 9, in each case with a different phase angle relative to the zero crossings of the carrier signal is taken as a basis for an individual demodulation operation. This number is limited upwardly only by practical conditions.
  • the invention may optionally also be combined with an electronically acting speed sensor 17 .
  • This option has the particular advantage that, in comparison with devices that are currently commercially available, it is possible to obtain a considerable saving of filter module sets for the purpose of further treatment of the demodulated signal(s) in the manner described below:
  • spectral components of the signal to be evaluated or demodulated are provided from a larger environment of the carrier frequency, and also the associated harmonics. This is based on the so-called indeterminacy principle. It is known that the environment or the respective line width, and thus, the desired demodulation result is inversely proportional to the number of samples presently used in each case.
  • a large number of samples is to be fed to a calculation (transformation, e.g., DFT, FFT or the like) that is presently to be performed in each case.
  • a calculation transformation, e.g., DFT, FFT or the like
  • the abovementioned indeterminacy principle likewise means that the attainable bandwidth is inversely proportional to the available measurement time assuming the normal situation of proportionality between the number of samples and the associated measurement time.
  • a small number of samples that is to say a short (effective) measurement time, is to be chosen.
  • the effective measurement time may, however, as explained above, be appropriately extended by a suitable intermittent or undersampling operation in order to meet the conditions of an A/D converter or the available computer power).
  • This sensor may be constructed in a simple manner known per se, e.g., by means of light barriers, such that a slow speed “v” of the test specimen supplies a low frequency speed signal which proportionally acquires a higher frequency as the speed increases.
  • a slow speed “v” of the test specimen supplies a low frequency speed signal which proportionally acquires a higher frequency as the speed increases.
  • a speed of 0.1 in/sec effects pulse lengths of 15,000 microseconds
  • a speed of 10 m/sec generates pulse lengths of the speed signal of only 150 microseconds, etc.
  • the desired filter effect on the already demodulated signal by taking the determined pulse length of the speed sensor as an essentially direct measure of the number of samples that are to be evaluated set by set in each case, so that, e.g., approximately only 75 samples are fed to a DFT or FFT in the last-mentioned case and, e.g., approximately 7500 samples in the former case.
  • the computational complexity in calculating Fourier transforms rises only subproportionally for an increasing number of samples, so that a skilful utilization of the computational capacity of the electronics provided can take place in the context according to the invention. It is useful to limit the number of measured values that are to be fed to a transformation in each case; at the very least—when the test specimen is at a standstill—a corresponding item of status information should be supplied by the speed sensor.
  • the transmission frequency can also be modified to a certain extent in that it is derived by integer division from a significantly higher-frequency time or frequency base.
  • the procedure may be such that the transmitting coil is energized only for a few full waves prior to detection of the sample in accordance with a desired transmission signal (in order to realize a transient recovery process) and is de-energized immediately after detection of the sample at an appropriately chosen point in time, a technically advantageous oscillation decay behavior of the transmitting coil being sought. This is advantageous particularly for battery-operated, portable devices.
  • FIGS. 15 to 18 show some results for visual evaluation as were obtained according to the invention using the information already taken as a basis in FIGS. 3 to 6 , 11 and 12 , that is to say in particular using the diverse amplitude and phase information.
  • the data of the carrier, of the first harmonic and of the second harmonic are used in multiple relation and concatenation.
  • FIG. 15 is based on the continuous evaluation of Fourier transformations which were carried out on the basis of all those samples that were also used for FIG. 3 , that is to say without a test specimen defect, and during a shorter time interval.
  • FIG. 16 shows a comparable illustration, based on the data also associated with FIGS. 5 and 11 (“intermittent” data acquisition in the manner of undersampling).
  • FIGS. 17 and 18 show the case when there is a defective test specimen surface, without and respectively with “intermittent” data acquisition (with chosen distance number equals 97 samples).
  • the envelope of the lines illustrated is of distinctly extended configuration and significantly different than in the case of FIGS. 15 and 16 .
  • FIG. 19 Another form of the result illustration is reproduced in FIG. 19 .
  • a suitably scaled logarithmic that is to say, e.g., decibel
  • the end points of the plotted values are connected to form a triangle, as shown.
  • FIG. 19 in this case, relates to the corresponding values from FIGS. 3 and 4 .
  • the logarithmic scale direction chosen remains free to be reversed, so that a triangle in the presence of a fault is represented larger than in the fault-free case.
  • FIGS. 15 to 19 are to be understood merely as examples of how acceptance or damage results calculated according to the invention can be visualized.
  • the number of visualization possibilities in comparison with modes of representation known heretofore for test methods of the type under consideration here is comparatively extensive and can be modified in an approximately arbitrary manner on account of the almost completely digital character of the fault identification proposed. It is thus also possible to perform a conventional representation with a correspondingly reduced information content if this is desirable for comparison purposes.
  • the data sets and information obtained according to the invention have to be fed to an expediently suitable pattern recognition device in order to be able to automatically drive external aids, such as fault marking devices, saws, etc.
  • the apparatus and methods according to the invention can be used with highly diverse sensor systems, in particular, ultrasonic and eddy current based sensor systems, but also with so-called EMAT systems, or systems which use so-called magneto-resistive sensors for detecting the eddy current fields.

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  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)
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US20100045276A1 (en) * 2007-01-25 2010-02-25 Board Of Trustees Of Michigan State University Eddy current inspection system
US20140266149A1 (en) * 2013-03-12 2014-09-18 Motorola Mobility Llc Cover-testing fixture for radio frequency sensitive devices
US8841902B2 (en) 2012-01-20 2014-09-23 Prüftechnik Dieter Busch AG Testing device and testing method for non destructive detection of a defect in a test piece by means of an eddy current

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DE102009022136A1 (de) 2009-05-20 2010-11-25 Prüftechnik Dieter Busch AG Vorrichtung und Verfahren für induktive Messungen
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CN102004209A (zh) * 2010-12-03 2011-04-06 丹东欣泰电气股份有限公司 配电网电缆故障在线测距装置及测距方法
AT511773A1 (de) * 2011-07-15 2013-02-15 Voestalpine Stahl Gmbh Vorrichtung und verfahren zur detektion wenigstens eines periodisch auftretenden fehlers an einem gegenstand
DE102011079438B4 (de) 2011-07-19 2013-09-12 Institut Dr. Foerster Gmbh & Co. Kg Verfahren und Vorrichtung zur zerstörungsfreien Werkstoffprüfung eines Prüflings
DE102012100460A1 (de) * 2012-01-20 2013-07-25 Prüftechnik Dieter Busch AG Prüfanordnung und Prüfverfahren zur zerstörungsfreien Erfassung eines Fehlers in einem Prüfling mittels eines Wirbelstroms
CN104062356A (zh) * 2013-03-22 2014-09-24 厦门艾帝尔电子科技有限公司 用于克服涡流电磁检测干扰信号判断缺陷的方法及其装置
RU2572791C2 (ru) * 2014-01-10 2016-01-20 Общество с ограниченной ответственностью "Константа" Способ оценки качества паяного соединения обмоток электрических машин
CN105389475B (zh) * 2015-12-22 2018-04-20 中国石油大学(华东) 一种基于小波包分解的电厂设备故障检测方法
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US20140266149A1 (en) * 2013-03-12 2014-09-18 Motorola Mobility Llc Cover-testing fixture for radio frequency sensitive devices

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DE112005002292A5 (de) 2007-07-12
DE502005007367D1 (de) 2009-07-09
US7423424B2 (en) 2008-09-09
EP1792173A1 (fr) 2007-06-06
DE112005002290A5 (de) 2007-07-12
EP1792173B1 (fr) 2015-07-08
US20070080681A1 (en) 2007-04-12
ATE432467T1 (de) 2009-06-15
US20070242758A1 (en) 2007-10-18
EP1794582B1 (fr) 2009-05-27
EP1794582A1 (fr) 2007-06-13
WO2006007832A1 (fr) 2006-01-26

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